Add resource information to logger of GKE, GCE and AWS EC2 (#180)

* Add resource information to logger of GKE, GCE and AWS EC2

* Remove env var. Add return error

* Handling error of stackdriver logger creation

* Handling error of stackdriver logger creation

* Docs for logID

* LogID Doc and use default values if is not provided

* Update error message

* Update doc

server/kit/kitserver.go

@@ -79,7 +79,7 @@ func NewServer(svc Service) *Server {
 
 	ctx := context.Background()
 
-	lg, logClose, err := NewLogger(ctx)
+	lg, logClose, err := NewLogger(ctx, "")
 	if err != nil {
 		stdlog.Fatalf("unable to start up logger: %s", err)
 	}

server/kit/log.go

@@ -9,22 +9,31 @@ import (
 	"google.golang.org/grpc/metadata"
 )
 
-// NewLogger will inspect the environment and, if running in the Google App Engine
-// environment, it will return a new Stackdriver logger annotated with the current
-// server's project ID, service ID and version. If not in App Engine, a normal JSON
-// logger pointing to stdout will be returned.
+// NewLogger will inspect the environment and, if running in the Google App Engine,
+// Google Kubernetes Engine, Google Compute Engine or AWS EC2 environment,
+// it will return a new Stackdriver logger annotated with the current
+// server's project ID, service ID and version and other environment specific values.
+// If not in App Engine, GKE, GCE or AWS EC2 - a normal JSON logger pointing to stdout
+// will be returned.
 // This function can be used for services that need to log information outside the
 // context of an inbound request.
 // When using the Stackdriver logger, any go-kit/log/levels will be translated to
 // Stackdriver severity levels.
-func NewLogger(ctx context.Context) (log.Logger, func() error, error) {
-	// running locally or in a non-GAE environment? use JSON
-	if !isGAE() {
-		return log.NewJSONLogger(log.NewSyncWriter(os.Stdout)), func() error { return nil }, nil
-	}
-
+// The logID field is used when the server is deployed in a Stackdriver enabled environment.
+// If an empty string is provided, "gae_log" will be used in App Engine and "stdout" elsewhere.
+// For more information about to use of logID see the documentation here: https://cloud.google.com/logging/docs/reference/v2/rest/v2/LogEntry#FIELDS.log_name
+func NewLogger(ctx context.Context, logID string) (log.Logger, func() error, error) {
 	projectID, serviceID, svcVersion := getGAEInfo()
-	return newAppEngineLogger(ctx, projectID, serviceID, svcVersion)
+	lg, cl, err := newStackdriverLogger(ctx, logID, projectID, serviceID, svcVersion)
+	// if Stackdriver logger was not able to find information about monitored resource it returns nil.
+	if err != nil {
+		// running locally or in a non-GAE environment? use JSON
+		lg := log.NewJSONLogger(log.NewSyncWriter(os.Stdout))
+		lg.Log("error", err,
+			"message", "unable to initialize Stackdriver logger. falling back to stdout JSON logging.")
+		return lg, func() error { return nil }, nil
+	}
+	return lg, cl, err
 }
 
 // Logger will return a kit/log.Logger that has been injected into the context by the kit

server/kit/gae_log.go → server/kit/sd_log.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"cloud.google.com/go/logging"
+	"contrib.go.opencensus.io/exporter/stackdriver/monitoredresource"
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
 	"github.com/pkg/errors"
@@ -27,34 +28,53 @@ func isGAE() bool {
 	return os.Getenv("GAE_DEPLOYMENT_ID") != ""
 }
 
-type gaeLogger struct {
+type sdLogger struct {
 	project string
 	monRes  *monitoredres.MonitoredResource
 	lc      *logging.Client
 	lgr     *logging.Logger
 }
 
-func newAppEngineLogger(ctx context.Context, projectID, service, version string) (log.Logger, func() error, error) {
+func newStackdriverLogger(ctx context.Context, logID, projectID, service, version string) (log.Logger, func() error, error) {
+	resource := &monitoredres.MonitoredResource{
+		Labels: map[string]string{
+			"module_id":  service,
+			"project_id": projectID,
+			"version_id": version,
+		},
+	}
+	if isGAE() {
+		resource.Type = "gae_app"
+		if logID == "" {
+			logID = "app_logs"
+		}
+	} else if mr := monitoredresource.Autodetect(); mr != nil {
+		typ, lbls := mr.MonitoredResource()
+		for f, v := range lbls {
+			resource.Labels[f] = v
+		}
+		resource.Type = typ
+		if logID == "" {
+			logID = "stdout"
+		}
+	} else {
+		return nil, nil, errors.New("unable to find monitored resource")
+	}
+
 	client, err := logging.NewClient(ctx, fmt.Sprintf("projects/%s", projectID))
 	if err != nil {
 		return nil, nil, errors.Wrap(err, "unable to initiate stackdriver log client")
 	}
-	return gaeLogger{
+
+	return sdLogger{
 		lc:      client,
-		lgr:     client.Logger("app_logs"),
+		lgr:     client.Logger(logID),
 		project: projectID,
-		monRes: &monitoredres.MonitoredResource{
-			Labels: map[string]string{
-				"module_id":  service,
-				"project_id": projectID,
-				"version_id": version,
-			},
-			Type: "gae_app",
-		},
+		monRes:  resource,
 	}, client.Close, nil
 }
 
-func (l gaeLogger) Log(keyvals ...interface{}) error {
+func (l sdLogger) Log(keyvals ...interface{}) error {
 	kvs, lvl, traceContext := logKeyValsToMap(keyvals...)
 	var traceID string
 	if traceContext != "" {
@@ -87,7 +107,7 @@ func (l gaeLogger) Log(keyvals ...interface{}) error {
 	return nil
 }
 
-func (l gaeLogger) getTraceID(traceCtx string) string {
+func (l sdLogger) getTraceID(traceCtx string) string {
 	return "projects/" + l.project + "/traces/" + strings.Split(traceCtx, "/")[0]
 }